The purpose of this project is to study the long-term health effects of therapeutic drugs as they may relate to carcinogenicity. Cohort studies of exposed groups are conducted, as well as case-control studies of selected cancer sites which involve lifetime drug use histories. Emphasis in the past year has been on the evaluation of various types of estrogenic preparations and immunosuppressive drugs. BIBLIOGRAPHIC REFERENCES: Hoover, R., Gray, L.A., Cole, P., and MacMahon, B.: Menopausal estrogens and breast cancer. N. Engl. J. Med. 295: 401-405, 1976. Gray, L.A., Christopherson, W.M. and Hoover, R.: Estrogens and endometrial carcinoma. Am. J. Obstet. Gynecol. 49: 385-389, 1977.